The practice of winding yarn onto tubular carriers during textile production is well known in the art. During high-speed production of yarn or thread, the continuously advancing yarn is wound onto consecutive rotating cores or tubes. As a rotating tube encounters a leading strand of the yarn, the tube frictionally engages the yarn to secure an initial wind of the yarn onto the tube and simultaneously break the yarn between the tube and the preceding tube. Therefore, it is important that the tube be able to successfully engage the leading strand of yarn to secure the yarn to the tube and to break the yarn from the preceding tube.
Conventional tubes often employ a relatively deep “start-up” groove for receiving the leading strand of yarn. The groove is typically “V” shaped and formed near one or both ends of the tube by forcing a wedged-shaped tool into the outside diameter surface of the tube. The groove has a “wide” section about a portion of the circumference of the tube so that the yarn can locate within the groove, and a “narrow” section for catching and breaking the yarn. Such a groove is disclosed in U.S. Pat. No. 5,328,121, which is assigned to the assignee of the present invention and incorporated herein by reference in its entirety. While the start-up grooves disclosed by the '121 patent have become an industry standard in the textile winding field, there are still improvements to be made.
In particular, it has been discovered that there are occasions where the yarn misses the wide target area of the groove and results in a failed start up, which causes production problems such as downtime and wasted material. There are several reasons why failed start ups occur, among them being (a) variation in yarn tension, (b) improper location of mechanical yarn guides, and (c) variation in groove dimensions. In addition, it has been discovered that the moisture content of the tube can have significant effects on the grooves, as most tubes are formed of paperboard and therefore are somewhat hygroscopic, i.e., capable of gaining and losing moisture. More specifically, a relatively high moisture content of the tube can cause the paperboard to swell, which effectively closes the V-shaped groove and makes successful start ups less likely. Because most textile winding operations are performed in large manufacturing facilities, controlling and maintaining the moisture content and temperature in the surrounding atmosphere is difficult. Thus, there is a need for a tube or core for winding yarn that is less reactive to humidity and other environmental conditions. There is also a need for a yarn tube that allows for easier yarn start-ups.
Some yarn tubes have attempted to improve catching the yarn by adding a relatively shallow, recessed score leading up to the relatively deep groove to help guide the yarn into the target area of the groove. While the addition of a shallow score appears to aid yarn start up compared to a groove-only configuration, adding the score creates complexity to the manufacturing process while failing to address the moisture problems that affect the V-shaped start up groove. In addition, all conventional start up grooves suffer from yarn and debris buildup and an eventual degradation of the surface of the groove. Conventional yarn tubes are thrown away when they begin failing to catch yarn, although this is quite wasteful. Thus, there is also a need to prolong the lifespan of a yarn tube in order to maximize the financial investment and maintain efficiency.